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As culls were repeated, the proportion of infected badgers increased prevalence (relative to first proactive) error bars show 95% CI RBCT culling led to a rapid drop in badger numbers… but numbers of infected badgers fell more slowly

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CULL Disrupts territorial system Increases opportunities for contact between social groups Increases opportunities for disease transmission Increases number of cattle herds contacted by each badger What badger culling actually does

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Removes susceptibles by making them immune No impact on those already infected Nevertheless, helped eradicate smallpox and rinderpest, and to control many other diseases e.g. measles, rabies, human TB

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What badger vaccination is meant to do No effect on already-infected animals Reduce onward transmission of infection vaccinate

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What vaccination is meant to do No effect on already-infected animals Reduce onward transmission of infection

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vaccinate What vaccination is meant to do No effect on already-infected animals Reduce onward transmission of infection Lowers prevalence over time as infected animals die off

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vaccinate What vaccination is meant to do No effect on already-infected animals Reduce onward transmission of infection Lowers prevalence over time as infected animals die off Population structure likely to enhance vaccine benefits

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no social perturbation social perturbation Catch and test 60-80% of badgers Detect and cull 49% of infected badgers Vaccinate test-negative badgers

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CSL (now AHVLA) 2009: “if... [selective] culling produced no social perturbation then the reduction in the number of infected badgers, and the reduction in herd breakdowns, was greater than either culling or vaccination... If... culling resulted in repeated perturbation of social groups each time a badger social group... had an animal culled, then there was a dramatic increase in the number of infected badgers and the number of herd breakdowns” Estimates of the threshold numbers of badgers culled needed to prompt increase in territory size Bielby et al (in prep) – effects of 1986-98 small-scale culls on badger populations in 1998-2002

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Conclusions Nonselective culling, vaccination, and selective culling function by different mechanisms but in principal all have the potential to control wildlife disease Population structure can have a major impact on disease transmission rates Culling alters badger population structure in ways which accelerate transmission, undermining benefits for TB control By contrast, badger population structure is likely to enhance the efficacy of vaccination Badger vaccination is likely to be cheaper than culling, and is unlikely to cause harm; however its contribution to cattle TB control is not yet known